Quoting the article http://www.jb51.net/article/58020.htm
Detailed explanation of awk regular expressions and built-in function examples:
1. Fuzzy matching:
awk '{if($3~/97/) print $0}' data.f: print this line if the third item contains "97"
awk '{if($4!~/ufcx/) print $0}' data.f: print if the third item does not contain ufcx
2. Exact match:
awk '{if($5==66) print $0}' data.f: print if the fifth item is 66
awk '{if($5!=66)print $0}' data.f : print if the fifth item is not 66
awk '{if($1>$5) print $0}' data.f: print if the first item is greater than the fifth item
3. Case matching:
awk '{if(/[Ss]ept/) print $0}' data.f: If it matches, print a line.
awk '/[Ss]ept/ {print $2}' data.f: if it matches, then print the second field
4. Any match:
awk '{if($2 ~/^.e/) print $0}' data.f: In the second field, the second character is e, output
awk '{if($4 ~/(lps|fcx)/) print $0}' data.f: output if the fourth field contains lps or fcx
5、&&，||：
awk '{if($3 ~/1993/ && $2==”sept”) print $0}' data.f: output if both sides are true
awk '{if($3 ~/a9/ || $2==”sept”) print $0}' data.f: output if one side is true
6. Variable definition:
awk '{date=$2;price=$5; if(date ~/[Ss]ept/) print “price is ” price}' data.f: variable definition, output price if date is sept or sept.
7. Modify the value (the value of the source file remains unchanged)
awk '{BASELINE=42; if($1>BASELINE) $5=$5+100; print $0}' data.f: three-line program, separated by ";"
If the modification is a text field, add """". For example: awk '{if($2==”may”) $2=”tt”; print $0}' data.f
above shows all data, awk '{if($2==”may”) {$2=” tt"; print $0}}' data.f This only shows the modified data. Take a closer look. In fact, the syntax is the same as c, except that a {} symbol is added to the outermost.
8. Create a new domain: (the value of the source file remains unchanged)
awk ‘{if($5>$1){$8=$5-$1;print $1,$8}}' data.f：
或者awk ‘{if($5>$1){diff=$5-$1;print $1,diff}}' data.f
9. Data statistics:
awk '{(total+=$5)}END{print total}' data.f: "{(total+=$5)}" and "{print total}" represent two different code segments, if not The cumulative result of END will be output every time, and END can be understood as the sign of the code paragraph, so that only the final result is output, that is, {print total} is executed only once.
10. Statistical file size:
ls –l | awk '{if(/^[^d]/) total=+$5}END{print "total KB:" total}': /^[^d]/ The field value $1 can be omitted for the first match of the line
11. Awk built-in variables:
ARGC Number of command-line parameters
ARGV Command-line parameter arrangement
ENVIRON Support system environment variables in the queue Use
FILENAME awk to browse the file name
FNR Browse the number of records in the file
FS Set the input field separator, which is equivalent to the command line -F option
NF number of fields browsed records
NR number of records read
OFS output field separator
ORS output record separator
RS control record separator
12, awk built-in string processing function
gsub ( r, s ) is used in the entire $0 s replaces r
gsub( r, s , t ) replaces r with s throughout t
index( s , t ) returns the first position of string t in
s length( s ) returns the length of s
match( s , r ) test s Whether it contains a string matching r, return position
split ( s , a , fs ) split s into sequence a on fs
sprint ( fmt , exp ) return fmt-formatted exp in
sub ( r, s , $0) $0 s replaces the first occurrence of r
substr ( s , p ) returns the suffix part of string s starting from p
substr ( s , p , n ) returns the suffix part of string s starting from p and having length n
13. awk 'gsub(/6\./,78) {print $0}' data.f: replace all "6." with 78, and output
awk '{if($2=="Sept") {sub( /3/,"9",$0); print $0}}' data.f: replace only the first occurrence of
awk 'BEGIN{print index("hello","lo")}': the output value is 4
awk '{if($3==”3BC1997″) print length($3) ” ” $3}' data.f
awk 'BEGIN{print match("ABCD","B")}': output 2
awk 'BEGIN{print match("ABCD",/B/)}': "//" and """" have the same effect
awk 'BEGIN {print split("123#234#654", myarray, "#")}': return an array The number of elements, 123#234#654 is a string, with "#" as the delimiter, put the string into the array.
awk '{if($1==34) print substr($3,2,7)}' data.f
awk 'BEGIN{print substr("helloleeboy",2,7)}': output ellole
awk 'BEGIN{print substr ("helloleeboy",2,7)}' data.f: output n times ellole, n is the number of lines in data.f
14, awk 'BEGIN{print "May\tDay\n\nMay \104\141\171" }' :\104\141\171 means Day. \t: tab key, \n: newline, \ddd: octal
15. echo "65" | awk '{printf "%c\n",$0}': printf function, similar to c, the output is A. (ASCII code)
echo "65" | awk '{printf "%d\n",$0}': output 65 digits.
awk '{printf "%-15s %s\n",$2,$3}' data.f: "%-15s" left justified 15 characters long
awk '{if(age<$1) print $0}' age=80 data.f and awk '{age=49;if(age<$1) print $0}' The result of data.f is the same, the former passes the value into awk, and the latter defines a variable in awk.